Maternity leave ending?!

I'm still on maternity leave I've been out since February 16th but I'm supposed to return by October 22nd. I was full time but I want to go back part time. Does my employer reserve the right to tell me that they don't have a part time position available, when I know they have positions? I work as a CNA at the hospital. I know they hired someone recently as a floater on our floor. So it makes me mad they would say this to me. Any advice would be helpful!!